DRIVE SYSTEM VIBRATION MAINTENANCE OPERATIONAL CHECK
Tool Kit, Powertrain
Aircraft Powertrain Repairer/NDI
Maintenance Test Pilot
Make sure that helicopter safing procedures are accomplished. Observe all
safety precautions during troubleshooting and maintenance procedures.
Failure to do so could result in death or serious injury.
Refer to pilot station (fig. 612) and CPG station (fig. 613) for cockpit
configuration and equipment.
If referenced out of one paragraph or volume and into another for
additional troubleshooting, upon completion of the task return to the
maintenance operational check for the original paragraph or volume.
1. Complete the maintenance operational check as follows:
a. Start and run helicopter
(TM 1-1520-238-CL). On pilot master
caution/warning panel (fig. 617), check that
LOW RPM ROTOR indicator goes out when
Nr RPM% on pilot ENGRTR RPM%
indicator (fig. 622) reaches or is above
If main rotor or tail rotor do not rotate, refer to
TM 1-1520-238-23 to visually inspect drive system.
If LOW RPM ROTOR indicator remains lighted above
93% Nr on pilot and CPG master caution/warning
panels, go to paragraph 682.
b. Increase power on one engine to 100%, and
then retard throttle slowly until Np vertical
scale reads 80% to 85% Np.